Boiling water reactor

Description

BACKGROUND OF THE INVENTION

TECHNICAL FIELD

[0001] The present invention relates to a boiling water reactor having a reactor pressure vessel equipped with an openable upper lid.

BACKGROUND ART

[0002] A typically known boiling water reactor will be described below by referring to FIG. 5. FIG. 5 is a schematic diagram of a known boiling water reactor, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the vent line and the head spray line thereof.

[0003] The vent line 21 of the reactor pressure vessel 1 of a conventional nuclear power plant is installed to exhaust gas and steam from or supply gas and steam to the inside of the reactor pressure vessel 1 when the nuclear reactor is shut down, and penetrates a reactor pressure vessel upper lid 2. The vent line 21 arranged at a top part of the reactor pressure vessel 1 includes a non-condensable gas exhaust line 23 arranged to exhaust non-condensable gas that can be accumulated in the top part of the reactor pressure vessel 1 while the nuclear reactor is operating. An end of the vent pipe is connected to a main steam pipe 20.

[0004] A head spray line 22 is branched from the vent line 21 as disclosed in Japanese Patent Application Laid-Open Publication No. 11-231088. When the nuclear reactor is shut down, the steam discharged from a dryer 26 can be cooled by spraying water into the gas phase section in the reactor pressure vessel upper lid 2 by way of the head spray line 22.

[0005] Documents US 4 093 513 A and JP 58 131590 A disclose through pipings that penetrate the lateral side of the main body trunk of the reactor vessel. The through pipings are connected to water sprinklers which are arranged higher than the upper open end of the main body trunk in the reactor pressure vessel.

[0006] Additionally, the water level in the inside of the reactor pressure vessel 1 needs to be raised and lowered when the nuclear reactor is started and shut down, and a reactor water level gauge 7 is provided to monitor the water level. An upper take-out point of the reactor water level gauge 7 is branched out from the top part of the reactor pressure vessel 1.

[0007] A water level gauge which is connected to a through piping which penetrates the lateral side of the main body trunk of the reactor vessel is known from Document JP 58-61498.

[0008] The fuel in the reactor core 34 in the reactor pressure vessel 1 keeps on emitting decay heat after the nuclear reactor is shut down. In order to remove the decay heat, the reactor water in the reactor pressure vessel 1 is partly taken out, pressurized by a reactor water circulation pump 16 and cooled by way of a reactor water cooling heat exchanger 17. Then, the cooled water is returned to the inside of the reactor pressure vessel 1.

[0009] Besides, water can be fed to the head spray line 22 from the downstream of the reactor water cooling heat exchanger 17. More specifically, steam can be cooled in the reactor pressure vessel 1 by partly utilizing the water to be returned to the reactor pressure vessel 1 so as to spray the water into the gas phase section in the reactor pressure vessel upper lid 2.

[0010] The piping of the reactor pressure vessel vent line 21 and the head spray line 22 is disposed on the heat insulating material 15 of the reactor pressure vessel 1. Therefore, the heat insulating material 15 cannot be removed unless the reactor pressure vessel flanges 24 are uncoupled and the piping on the reactor pressure vessel upper lid 2 is taken away.

[0011] It is required to reduce the shut down period of the nuclear reactor of a nuclear power plant in order to improve the operation rate of the power plant. In recent years, the head spray line has been employed to cool the upper part of the nuclear reactor in order to improve the cooling rate of the nuclear reactor and to open the reactor pressure vessel as soon as possible.

[0012] When the nuclear reactor is shut down and the temperature of the reactor water is 100 degrees Celsius or higher, the piping connected to the reactor pressure vessel 1 cannot be removed because the inside of the reactor pressure vessel upper lid 2 is filled with steam. The heat insulating material 15 of the reactor pressure vessel 1 cannot be removed in such a condition.

[0013] Therefore, in order to open the reactor pressure vessel 1 early, it is desirable to remove the reactor pressure vessel heat insulating material 15 early and, when the reactor water temperature falls well below 100 degrees Celsius, quickly take away the reactor pressure vessel upper lid 2.

[0014] To take away the reactor pressure vessel upper lid 2, the operation of loosening the stud bolts 11 tightly binding the reactor pressure vessel flanges 5 together needs to be conducted quickly. However, since the head spray line 22 is not so designed as to directly spray water to the inner wall of the reactor pressure vessel 1, it takes time to cool the reactor pressure vessel 1 even by using the head spray line 22.

SUMMARY OF THE INVENTION

[0015] In view of the above-identified circumstances, it is therefore an object of the present invention to make it possible to open the reactor pressure vessel upper lid of a boiling water reactor early when the reactor is shut down.

[0016] According to the present invention, there is provided a boiling water reactor according to claim 1. Further embodiments are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other features and advantages of the present invention will become apparent from the discussion hereinbelow of specific, illustrative embodiments thereof presented in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of the first embodiment of boiling water reactor according to the present invention, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the vent line thereof;

FIG. 2 is a schematic diagram of the second embodiment of boiling water reactor according to the present invention, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the head spray line thereof;

FIG. 3 is a schematic partial cross-sectional elevational view of the head spray line of FIG. 2, showing the configuration thereof;

FIG. 4 is a schematic partial cross-sectional plane view of the head spray line of FIGS. 2 and 3 showing the configuration thereof; and

FIG. 5 is a schematic diagram of a known boiling water reactor, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the vent line and the head spray line thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Now, embodiments of the boiling water reactor according to the present invention will be described below by referring to FIGS. 1 through 4. The components same as or similar to those of the conventional art shown in FIG. 5 are denoted by the same reference symbols and will be not described repeatedly.

[First Embodiment]

[0019] The vent line in the inside of the reactor pressure vessel of this embodiment will be described below. FIG. 1 is a schematic diagram of the first embodiment of the boiling water reactor according to the present invention, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the vent line thereof.

[0020] A containment vessel 30 is partitioned to form a dry well 31 and a wet well 32 that communicate with each other. A reactor pressure vessel 2 is disposed in the dry well 31. A suppression pool 33 is disposed in the wet well 32.

[0021] The reactor pressure vessel 1 is a substantially cylindrical container with a vertical axis, and has a main body trunk 38 with an upper open end formed at the top thereof and a pressure vessel upper lid 2 arranged to cover the upper open end. The junction of the main body trunk 38 and the pressure vessel upper lid 2 has a flange structure such that the main body trunk flange 5a formed at the upper end of the main body trunk 38 and the upper lid flange 5b formed at the lower end of the pressure vessel upper lid 2 are coupled together by means of a plurality of stud bolts 11. The pressure vessel upper lid 2 is covered at the outside thereof with a heat insulating material 15. Although not shown, the main body trunk 38 is also covered by a heat insulating material at the periphery thereof.

[0022] A reactor core 34, separators 27 and dryers 26 are arranged in the reactor pressure vessel 1. At least the reactor core 34 and the separators 27 are disposed below the main body flange 5a.

[0023] A main steam pipe 20 is connected to the main body trunk 38 and a valve 18 (normally open) is arranged at an intermediate position thereof.

[0024] A reactor pressure vessel vent line 3 penetrates the main body trunk 38. The reactor pressure vessel vent line 3 extends upward along the inner wall surface of the reactor pressure vessel upper lid 2 in the reactor pressure vessel 1.

[0025] The reactor pressure vessel vent line 3 is connected to a condensation tank 8 for the reactor water level gauge by gas phase piping 40 extending substantially horizontally outside the reactor pressure vessel 1. Water piping 41 extending downward from the condensation tank 8 passes through the reactor water level gauge 7 and is connected to the reactor pressure vessel 1 below the gauge 7. Piping 42 branched from the gas phase piping 40 is connected to a dry well sump 6 through a drain valve 19 (normally closed). Piping 43 branched from the piping 42 at the downstream side (lower side) of the drain valve 19 is connected to a vacuum breaker 28. Piping 44 branched from the piping 42 at the downstream side of the drain valve 19 is connected to the suppression pool 33 by way of a valve 45 (normally closed).

[0026] A nitrogen gas filling line 50 is branched from the gas phase piping 40 at an intermediate position thereof so that nitrogen gas can be supplied from a nitrogen gas cylinder 9 to the gas phase piping 40 by way of a nitrogen gas supply valve 52.

[0027] With the above described arrangement of the reactor pressure vessel vent line 3, the reactor pressure vessel vent line 3 can be used to raise the water level in the reactor pressure vessel 1 at the time of a pressure resistance test or an operation of filling the nuclear reactor with water without penetrating the reactor pressure vessel upper lid 2.

[0028] Additionally, since the reactor pressure vessel upper lid 2 is free from any penetrations, the heat insulating material 15 of the reactor pressure vessel upper lid 2 and the reactor pressure vessel vent line 3 do not interfere with each other. Therefore, the heat insulating material 15 of the reactor pressure vessel upper lid 2 can be taken off to open the reactor pressure vessel 1 early while the nuclear reactor is under depressurization after it is shut down. The vent line is installed in the reactor pressure vessel upper lid 2 and is connected to the piping 40 that penetrates the main body trunk 38 below the main body trunk flange 5a at flanges 4. If the water level of the nuclear reactor is raised only to the vicinity of the level of the main body trunk flange 5a, it can be so arranged that the opening of the vent line is positioned at or above the level of the main body trunk flange 5a and no vent is formed at the reactor pressure vessel upper lid 2.

[0029] Steam can be prevented from dispersing from the inside of the dry well 31 when the vent of the reactor pressure vessel is opened, by connecting the discharge line to the dry well sump 6 at the time of venting the reactor pressure vessel 1.

[0030] Alternatively, the steam from the reactor pressure vessel vent line 3 can be discharged into the suppression pool 33 that is operated as heat sink in case of accident, instead of discharging the steam into the dry well sump 6

[0031] The reactor water level gauge 7 is arranged to monitor the water level when the reactor water level is raised or lowered during start up or shut down operation of the nuclear reactor. Because of this arrangement, the vent line 3 can be connected to the condensation tank 8 disposed at the reactor water level gauge 7, utilizing the vent line 3 as upper taking out point for gauging the water level by the reactor water level gauge 7. The reference water level can be held to a constant value by opening the drain valve 19.

[0032] When the nuclear reactor is shut down and the reactor water level is raised, nitrogen gas can be fed into the reactor pressure vessel vent line 3 by way of the nitrogen gas filling line 44 and fill the vent line 3 with nitrogen gas in order to replace steam with nitrogen gas so as to raise the water level stably. By filling with nitrogen gas, the non-condensable gas accumulated in a top part of the reactor pressure vessel 1 can be diluted and replaced when the nuclear reactor is shut down.

[Second Embodiment]

[0033] FIG. 2 is a schematic diagram of the second embodiment of boiling water reactor according to the present invention, showing a cross-sectional elevation of a principal part of the reactor pressure vessel and the system configuration of the head spray line thereof. FIG. 3 is a schematic partial cross-sectional elevational view of the head spray line of FIG. 2, showing the configuration thereof. FIG. 4 is a schematic partial cross-sectional plane view of the head spray line of FIGS. 2 and 3, showing the configuration thereof.

[0034] The head spray line in the inside of the reactor pressure vessel of this embodiment will be described below.

[0035] The reactor pressure vessel head spray line 10 penetrates the lateral side of the main body trunk 38 and not the reactor pressure vessel upper lid 2.

[0036] Additionally, spray nozzles 12 may be arranged so as to directly spray water toward the inner surface of the main body trunk flange 5a and that of the upper lid flange 5b from the head spray line 10 in order to improve the rate of cooling the nuclear reactor when the nuclear reactor is shut down. The head spray line 10 is installed in the reactor pressure vessel upper lid 2 and connected to the piping penetrating the main body trunk 38 at the flanges 4. The spray nozzles 12 are directed obliquely downward so that the sprayed water hits the inner wall surface of the reactor pressure vessel 1 to form a liquid film on the wall surface and cool the wall surface.

[0037] When the nuclear reactor is cooled, if the temperature of the stud bolts 11 that tightly bind the flanges of the reactor pressure vessel 1 including the main body trunk flange 5a and the upper lid flange 5b together falls slowly, operation of loosening the stud bolts 11 to open the reactor pressure vessel 1 cannot be started early, because such an operation cannot be conducted until the temperature of the stud bolts 11 falls sufficiently. However, in this embodiment, the flanges 5a and 5b can be cooled at an accelerated rate by arranging spray nozzles 12 for spraying water to the insides of the flanges 5a and 5b at the head spray line 10.

[0038] Similarly, spray nozzles 13 may be arranged so as to directly spray water toward the inner wall surface of the reactor pressure vessel upper lid 2 located above the flanges 5a and 5b and cool the steam in the inside of the reactor pressure vessel upper lid 2 at an accelerated rate when the nuclear reactor is cooled. Additionally, a liquid film is formed at the insides of the flanges 5a and 5b to cool the flanges as the water sprayed to the reactor pressure vessel upper lid 2 flows down. Furthermore, spray nozzles 12 may be installed separately.

[0039] Spray nozzles 14 for spraying water to the gas phase section in the inside of the reactor pressure vessel upper lid 2 may be installed as part of the spray nozzles for discharging water from the head spray line 10 in order to absorb sensible heat of steam. Spray nozzles 13 for cooling the reactor pressure vessel upper lid 2 and spray nozzles 12 for cooling the inside parts of the flanges 5 may be installed separately.

[0040] Thus, since the reactor pressure vessel upper lid 2 of this embodiment is free from any penetrations, the heat insulating material 15 on the reactor pressure vessel and the reactor pressure vessel vent line do not interfere with each other so that the heat insulating material 15 can be taken off to open the reactor pressure vessel early while the nuclear reactor is shut down and subsequently depressurized.

[Other Embodiments]

[0041] The above-described embodiments are only examples and the present invention is by no means limited to them.

[0042] For instance, as for the connections of the reactor pressure vessel vent line 3 outside the reactor pressure vessel 1 of the first embodiment, it may not necessarily be connected to all of , the nitrogen gas filling line 50, the dry well sump 6 and the suppression pool, and may be connected only to some of them.

[0043] Additionally, all the nozzles of the head spray line 10 of the second embodiment including the spray nozzle 12 for cooling the insides of the flanges, the spray nozzles 13 for cooling the reactor pressure vessel upper lid and the spray nozzles 14 for cooling the gas phase section of the reactor pressure vessel upper lid may not necessarily be installed, and only some of them may be installed.

[0044] Finally, any of the variously combined arrangements of the reactor pressure vessel vent line 3 of the first embodiment and any of the variously combined arrangements of the head spray line 10 of the second embodiment may be appropriately combined and connected.

Claims

1. A boiling water reactor comprising:

a reactor pressure vessel (1) that includes a main body trunk (38) having an upper open end and an openable upper lid (2) covering the upper open end of the main body trunk (38) from above; and

a through piping (3) that penetrates a lateral side of the main body trunk (38) and has an opening section at a same level with or higher than the upper open end of the main body trunk (38) in the reactor pressure vessel (1)

characterized in that said boiling water reactor further comprises:

a containment vessel (30) that includes a dry well (31) for containing the reactor pressure vessel (1), and a wet well (32) having a suppression pool (33) and communicating with the dry well (31); and

a water level gauge (7) arranged in the dry well (31) and outside the reactor pressure vessel (1), wherein the through piping (3) is connected to the water level gauge (7).

2. The boiling water reactor according to claim 1, further comprising
a sump (6) arranged In the dry well (31) and outside the reactor pressure vessel (1), wherein
the through piping (3) is connected to the sump (6).

3. The boiling water reactor according to claims 1 or 2, wherein
the through piping (3) is connected to the suppression pool

4. The boiling water reactor according to anyone of claims 1 through 3, wherein
the through piping (3) is connected to a line for injecting nitrogen gas outside the reactor pressure vessel (1).

5. The boiling water reactor according to anyone of claims 1 through 4, wherein
the through piping (3) is connected to a head spray line (3) for supplying spray water for cooling the upper lid (2) from inside into the reactor pressure vessel (1).

6. The boiling water reactor according to claim 5, wherein
the head spray line (3) is so arranged as to directly spray water to the inner surface of the upper lid (2).

7. The boiling water reactor according to claim 5, wherein
the main body trunk (38) and the upper lid (2) are coupled together at a junction that has a flange structure such that a main body trunk flange (5a) and an upper lid flange (5b) are coupled together, and
the head spray line (3) is so arranged as to directly spray water to inner surface of the main body trunk flange (5a) and inner surface of the upper lid flange (5b).

8. The boiling water reactor according to anyone of claims 5 through 7, wherein
the head spray line (3) is so arranged that the spray water is partly jetted out upwardly in the reactor pressure vessel (1).

Ansprüche

1. Siedewasserreaktor, umfassend:

einen Reaktordruckbehälter (1), der einen Hauptkörperrumpf (38) mit einem oberen offenen Ende und einen aufmachbaren oberen Deckel (2), der das obere offene Ende des Hauptkörperrumpfs (38) von oben her abdeckt, umfasst; und

eine Durchgangsverrohrung (3), die eine laterale Seite des Hauptkörperrumpfs (38) durchdringt und einen Öffnungsabschnitt aufweist, der sich in der gleichen Ebene wie oder höher als das obere offene Ende des Hauptkörperrumps (38) in dem Reaktordruckbehälters (1) befindet,

dadurch gekennzeichnet, dass der Siedewasserreaktor ferner Folgendes umfasst:

einen Sicherheitsbehälter (30), der ein Drywell (31) zur Aufnahme des Reaktordruckgefäßes (1) und ein Wetwell (32), das ein Druckabbaubecken (33) aufweist und mit dem Drywell (31) in Verbindung steht, umfasst; und

einen Wasserstandsanzeiger (7), der in dem Drywell (31) und außerhalb des Reaktordruckbehälters (1) angeordnet ist, wobei die Durchgangsverrohrung (3) mit dem Wasserstandsanzeiger (7) verbunden ist.

2. Siedewasserreaktor nach Anspruch 1, ferner umfassend:

einen Sumpf (6), der in dem Drywell (31) und außerhalb des Reaktordruckbehälters (1) angeordnet ist, wobei die Durchgangsverrohrung (3) mit dem Sumpf (6) verbunden ist.

3. Siedewasserreaktor nach Anspruch 1 oder 2, wobei
die Durchgangsverrohrung (3) mit dem Druckabbaubecken verbunden ist.

4. Siedewasserreaktor nach einem der Ansprüche 1 bis 3, wobei
die Durchgangsverrohrung (3) außerhalb des Reaktordruckbehälters (1) mit einer Leitung zum Einspritzen von Stickstoffgas verbunden ist.

5. Siedewasserreaktor nach einem der Ansprüche 1 bis 4, wobei
die Durchgangsverrohrung (3) mit einer Kopfsprühleitung (3), um Sprühwasser zur Kühlung des oberen Deckels (2) von innen her in den Reaktordruckbehälter (1) zu liefern, verbunden ist.

6. Siedewasserreaktor nach Anspruch 5, wobei
die Kopfsprühleitung (3) so angeordnet ist, dass sie Wasser direkt zu der Innenfläche des oberen Deckels (2) sprüht.

7. Siedewasserreaktor nach Anspruch 5, wobei
der Hauptkörperrumpf (38) und der obere Deckel (2) an einer Verbindungsstelle miteinander gekoppelt sind, die einen derartigen Flaschaufbau aufweist, dass ein Hauptkörperrumpfflansch (5a) und ein Flansch (5b) des oberen Deckels miteinander gekoppelt sind, und
die Kopfsprühleitung (3) so angeordnet ist, dass sie Wasser direkt zu der Innenfläche des Hauptkörperrumpfflanschs (5a) und der Innenfläche des Flanschs (5b) des oberen Deckels sprüht.

8. Siedewasserreaktor nach einem der Ansprüche 5 bis 7, wobei
die Kopfsprühleitung (3) so angeordnet ist, dass das Sprühwasser teilweise nach oben in den Reaktordruckbehälter (1) ausgestoßen wird.

Revendications

1. Réacteur à eau bouillante comprenant :

une cuve sous pression de réacteur (1) qui comprend un tronc de corps principal (38) présentant une extrémité supérieure ouverte et un couvercle supérieur ouvrable (2) couvrant l'extrémité supérieure ouverte du tronc de corps principal (38) par le dessus ; et

un conduit traversant (3) qui pénètre un côté latéral du tronc de corps principal (38) et présente une section d'ouverture à un même niveau que, ou plus haut que, l'extrémité supérieure ouverte du tronc de corps principal (38) dans la cuve sous pression de réacteur (1),

caractérisé en ce que le réacteur à eau bouillante comprend en outre
une cuve de confinement (30) qui comprend un volume d'expansion (31) pour confiner la cuve sous pression de réacteur (1), et un volume de condensation (32) présentant une piscine de suppression (33) et communiquant avec le volume d'expansion (31) ; et
une jauge de niveau d'eau (7) agencée dans le volume d'expansion (31) et hors de la cuve sous pression de réacteur (1), sachant que le conduit traversant (3) est relié à la jauge de niveau d'eau (7).

2. Réacteur à eau bouillante selon la revendication 1, comprenant en outre un puisard (6) agencé dans le volume d'expansion (31) et hors de la cuve sous pression de réacteur (1), sachant que le conduit traversant (3) est relié au puisard (6).

3. Réacteur à eau bouillante selon la revendication 1 ou 2, dans lequel le conduit traversant (3) est relié à la piscine de suppression.

4. Réacteur à eau bouillante selon l'une quelconque des revendications 1 à 3, dans lequel le conduit traversant (3) est relié à une ligne pour injecter de l'azote hors de la cuve sous pression de réacteur (1).

5. Réacteur à eau bouillante selon l'une quelconque des revendications 1 à 4, dans lequel le conduit traversant (3) est relié à une ligne d'arrosage de tête (3) pour fournir de l'eau à pulvériser pour refroidir le couvercle supérieur (2) par l'intérieur dans la cuve sous pression de réacteur (1).

6. Réacteur à eau bouillante selon la revendication 5, dans lequel la ligne d'arrosage de tête (3) est agencée de manière à pulvériser l'eau directement sur la surface intérieure du couvercle supérieur (2).

7. Réacteur à eau bouillante selon la revendication 5, dans lequel le tronc de corps principal (38) et le couvercle supérieur (2) sont couplés ensemble à une jonction qui présente une structure de bride telle qu'une bride du tronc de corps principal (5a) et une bride du couvercle supérieur (5b) sont couplées ensemble, et
la ligne d'arrosage de tête (3) est agencée de manière à pulvériser l'eau directement sur la surface intérieure de la bride du tronc de corps principal (5a) et la surface intérieure de la bride du couvercle supérieur (5b).

8. Réacteur à eau bouillante selon l'une quelconque des revendications 5 à 7, dans lequel la ligne d'arrosage de tête (3) est agencée de manière à ce que l'eau à pulvériser gicle partiellement vers le haut dans la cuve sous pression de réacteur (1).

Drawing